REVscene - Vancouver Automotive Forum

sonick · 03-17-2010, 09:07 PM

As title says. I upgraded a 300W max Pioneer 4ch amp to a 400W RMS MTX 4ch amp, and now I am getting alternator whine from the front speakers where there wasn't before with the old Pioneer amp.

When I unplug the front RCA's from the HU, I still get alternator whine. When I unplug the RCA's from the amp, the whine stops.

The loudness of the whine does not increase or decrease with the volume of the HU. If I turn it down to 1, the whine stays the same loudness.

What is likely the problem here? The only thing that's changed is the amp, everything else is the same as previous where I had no alternator whine.

Note that the ground wire for the amp is a higher gauge than the amp, could this be an issue? This is in an E30 BMW.

Thanks!

catalin · 03-17-2010, 11:24 PM

Well since you still have a whine with the rca's plugged then I would say that it's entering somewhere along the way where the rca's are run.
You could try a new rca on the outside of the vehicle and see if it's gone?
Higher gauge ground wire should be of no issue at all.

orgasm_donor · 03-17-2010, 11:48 PM

I have had noise issues with some MTX amps in the past. You may have ground loop issues which can be addressed fairly easily. How good are your RCAs? If they are really cheap and unshielded then that could be a problem too.

sonick · 03-18-2010, 07:18 AM

Thanks guys. The next step when I get home is to hook up my iPod via RCA to see if I get the same result to see if it's the amp or the RCA. Hopefully it is the RCA.

My RCA's are the Canadian Tire ones, but twisted pair (http://www.canadiantire.ca/AST/brows...252B12-ft..jsp). Are the Stinger wires from Visions any good? http://www2.visions.ca/Catalogue/Cat...productId=2294

s.t.k. · 03-18-2010, 07:42 AM

Stinger's pretty good!

Phil@rise · 03-18-2010, 10:55 AM

If its a new issue it will not be a pre amp cable or pre amp cable routing issue unless you fucked them up when unplugging them.
It is one thing. A ground loop issue. Your old pioneer was possibly better adapt to dealing with a ground loop noise issue. It most likely had better noise chokes in it.There's other causes but I cant chopstick type that much. If you like we are in Richmond as well and I can have a quick look at it for you and offer some further advice.

sonick · 03-18-2010, 11:09 AM

Quote:

Originally Posted by Phil@rise

If its a new issue it will not be a pre amp cable or pre amp cable routing issue unless you fucked them up when unplugging them.
It is one thing. A ground loop issue. Your old pioneer was possibly better adapt to dealing with a ground loop noise issue. It most likely had better noise chokes in it.There's other causes but I cant chopstick type that much. If you like we are in Richmond as well and I can have a quick look at it for you and offer some further advice.

Are you open on the weekends? I am going to play with the ground point tonight, and if I can't get it figured out I can try and drop by this weekend.

Just promise you won't kill me and dispose of my body lol.

Phil@rise · 03-18-2010, 11:18 AM

Quote:

Originally Posted by sonick

Are you open on the weekends? I am going to play with the ground point tonight, and if I can't get it figured out I can try and drop by this weekend.

Just promise you won't kill me and dispose of my body lol.

If I charge you and your don't pay I might have to fire up the chain saw but you in luck I don't intend on charging you.
I'll be here saturday for a few hours after 11

sonick · 03-18-2010, 08:23 PM

Update!

So I made the ground from the amp way shorter (8 or 10 inches) screwed into bare metal, no luck.

Hooking my iPod directly to amp via RCA produces NO alternator whine. This should be good news.

Hooking up a standard home RCA audio cable directly from HU to amp results in alternator whine.

Dude at Visions, when I was looking to get a Ground Loop Isolator was no help, and just assumed my amp was broken.

orgasm_donor · 03-18-2010, 09:39 PM

Quote:

Originally Posted by sonick

Update!

So I made the ground from the amp way shorter (8 or 10 inches) screwed into bare metal, no luck.

Hooking my iPod directly to amp via RCA produces NO alternator whine. This should be good news.

Hooking up a standard home RCA audio cable directly from HU to results in alternator whine.

Dude at Visions, when I was looking to get a Ground Loop Isolator was no help, and just assumed my amp was broken.

If you are ever in the Coq area we can always try a GLI for you to see if that works. No charge for the test.

Cman333 · 03-19-2010, 12:58 PM

Try some better RCA's and/or rerun then RCA's

sonick · 03-19-2010, 01:02 PM

I'm planning to swing by your guys' shop Saturday to take a look (around 11 as per Phil's post), would you have a set of RCA's and/or a GLI that I can test out?

sonick · 03-20-2010, 05:18 PM

Well, took it to RISE and Phil found that the positive battery clamp was basically FUBAR'd. Had it replaced and it seems to have fixed the hard-start issue I've been having lately.

However, I still have alternator whine. It is not noticeable 90% of the time, but in times where I'm stopped and it's a quiet part of a song, it is noticeable.

Tried grounding the deck directly to the same ground point as the amp, but still gets noise.

Phil@rise · 03-20-2010, 06:50 PM

Quote:

Originally Posted by sonick

Well, took it to RISE and Phil found that the positive battery clamp was basically FUBAR'd. Had it replaced and it seems to have fixed the hard-start issue I've been having lately.

However, I still have alternator whine. It is not noticeable 90% of the time, but in times where I'm stopped and it's a quiet part of a song, it is noticeable.

Tried grounding the deck directly to the same ground point as the amp, but still gets noise.

So the noise is still there a bit eh.
I'm thinking the noise is induced in your head unit possibly even a problem with the car. My reasoning for thinking so is because the noise seemed to be dependent with volume. As you turned up the volume or down the noise got louder and quieter respectively. Next time your in the area pop by I'll test the output of the alternator for AC voltage. If there is AC voltage present and if your deck doesn't have a proper noise choke on it then the noise will come through your deck into your amps and out your speakers.
It's a quick ten second test no appointment needed.

sonick · 03-22-2010, 07:27 AM

Hey Phil,

It may be a different noise we are hearing. There is a HISS that DOES change with volume, but that doesn't bother me. There is another alternator whine/buzz that is present and at the same loudness no matter what the volume.

At "1", the noise is just as loud as if it were at "30" and also persists when it is on PAUSE. However, it goes away at "0" as I think the HU cuts output altogether at "0". It gets louder with the headlights on.

It just occured to me to try and connect the iPod to the amp VIA the current RCA to test for sure whether it's the cable that is the culprit. Will have to try that when I get home tonight.

I shorted the RCA's on the amp and that was quiet, so I know 100% the amp is good. I really hope it's not the HU itself as it is brand new and it is really good lol.

Phil@rise · 03-22-2010, 12:27 PM

Swing by I'll take a listen and see if I can tell you what the culprit is.